Line-forming mechanism for typewriting machines



Feb. 23, 1954 CANHAM 2,670,067

LINE-FORMING MECHANISM FOR TYPEWRITING MACHINES Filed May 15, 1951 4 Sheets-Sheet 1 F i G. 1

INVENTOR Georgei Canham BY Feb. 23, 1954 CANHAM 2,670,067

LINE-FORMING MECHANISM FOR TYPEWRITING MACHINES 4 Sheets-Sheet 5 Filed May 15, 1951 INVENTOR Georgeffanizam BY fl M ATTO R N EYS Feb. 23, .1954 G, CANHAM 2,670,067

LINE-FORMING MECHANISM FOR TYPEWRITING MACHINES Filed May 15, 1951 4 Sheets-Sheet 4 FIG.5

INVENTOR Georgei Canlzam Patented Feb. 23, 1954 LINE-FORMING MECHANISM FOR TYPEWRITING MACHINES George E. Canham, West Orange, N. J., assignor to Ralph C. Coxhead Crp., Newark, N. J., a

corporation of Delaware Application May 15, 1951, Serial No. 226,368

16 Claims.

This invention relates to typewriting machines particularly adapted for type composition and, more particularly, to a machine for composing forms or lists which are to be reproduced. While the invention as illustrated is embodied in a composing machine known in the trade as the Varityper, the invention in its broader aspects is applicable to other typewriting machines as well.

In composing forms on the Varityper, various sizes and styles of type are available and may be readily interchanged so as to produce legible and attractive-appearing forms and lists. The present invention is directed to the provision of means for rapidly and easily typing leaders (a row of dots or dashes to carry the eye between two columns of print) or rules (full lines) with a typewriter, which lines compare favorably in appearance with those produced by set type or by ruling a photographic negative made from typed copy.

Among the objects of the invention are to provide a typewriting machine that will form leaders, rules, and double rules; that will form such lines automatically without the necessity of hitting a key for each impression; that will stop automatically when the line is completed; and to provide such a construction on a rear-strike typewriter such as the Varityper.

Other objects of the invention are to provide a generally improved mechanism for rapidly and easily inserting leaders and rules during the composition of a form or list, and to provide such a mechanism that is simple and dependable in operation and that will produce lines of good uniformity and proper contrast.

Further objects and objects relating to details and economies of construction, manufacture, and use will more definitely appear from the detailed description to follow.

The Varityper is a typewriting machine of the rear-strike variety, in which raised type symbols are formed on the cylindrical surface of a type shuttle which is mounted in front of a paper carriage adapted to be moved past the printing point. The shuttle, which is mounted for rotation about its axis, is rotated to index any selected symbol at the printing point, and a type ribbon is passed between the shuttle and the carriage. The carriage is of the open ty e, in which both the front and the back of the paper are exposed at the printing point and a hammer located behind the carriage moves forwardly to strike the paper against the ribbon and shuttle to form the printed impression.

In the form shown of the present invention,

leader dots or ruled-line segments are formed on the type shuttle, preferably being indexed at the printing point when the shuttle is in its normal position (not indexed for printing of symbols controlled by the keys). Mechanism is provided for successively operating the hammer and the carriage-spacing mechanism so as to rapidly form a series of type impressions of the sort desired across the paper. In conjunction with this mechanism, an automatic stop is provided to dis able the impression-forming mechanism at any desired point. Preferably, the control mechanism is electrical, the hammer mechanism and spacing mechanism being operated or released by a solenoid and an electrical circuit to the solenoid being successively interrupted to cause successive operation of the solenoid, each operation of the solenoid causing the symbol to be printed a single time. An electric switch actuated by a cam settable along the length of the carriage serves to open the circuit when the carriage has reached a predetermined point, so as to stop printing of the line at any desired point.

My invention is clearly defined in the appended claims. In the claims, as well as in the description, parts are at times identified by specific names for clarity and convenience, but such nomenclature is to be understood as having the broadest meaning consistent with the context and with the concept of my invention as distinguished from the pertinent prior art. The best form in which I have contemplated applying my invention is illustrated in the accompanying drawings forming part of this specification, in which:

Fig. 1 is a top plan view of a typewriter according to the present invention, portions of the typewriter being broken away or omitted for clarity and convenience of illustration.

Fig. 2 is a sample form illustrating the kinds and quality of leaders and rules that can be formed by the machine of the present invention.

Fig. 3 is a side elevation of a portion of the type shuttle.

Fig. 4 is a top plan view of the type shuttle portion shown in Fig. 3.

Fig. 5 is a wiring diagram of the hammer release control mechanism of the present invention.

Fig. 6 is a somewhat diagrammatic perspective view of the mechanical linkage for operating the hammer and controlling the spacing mechanism in connection with the printing of leaders and rules.

Fig. 7 is a somewhat diagrammatic fragmentary elevation of the mechanism for sup ressing the hammer action when printing leaders and rules.

Fig. 3 is a somewhat diagrammatic elevation of the switch and associated parts for automatically terminating a line at any desiredpoint."

Referring now to Fig. 1, the general organization of the typewriter with which the present invention is associated will be briefly described This typewriter, which is known to thetradeas a Varityper, has a frame l I for supporting the" various component parts of the machine. A' housing [2 covers the frame and most of the interior moving parts of the machine to protect" bossed in three rows upon a type shuttle 2i mounted for oscillation along the cylindrical surface of an anvil 22, so as to 'selectively'present characters at the printing'point. One row or case of embossed type characters is normally opposite the printing point, and'the' other two rows of charactersare movedto p'ositionoppo site the printing point by operation'of the-cap-ita'l'and figure shiftkeys to raise'the anvil and shuttle.

Ahammer 25' coacts with the type shuttle 2! to drive paper interposed therebetween against the shuttle at the printing point "in order to'form a type impression. A pigment'ribbon'26 is'interposed between the paper and 'the'shuttle 2! to supply ink for the printing operation.

The paper is carried'past the printing point 20 and supported in position between the shuttle 2| and the hammer by'a movable paper car riage 27, this carriage progressing'a short dis tance after each printing impression or'for spac ing between words in order to" properly space the printed characters.

The carriage 27 'is mounted on guiderailsKnot shown) and is biased towards the left; its"'movement towards the left being'restrained by an escapement mechanism which is" actuated up'o'n' forming a printed impression so as to release the carriage for-movement a" short" distance'in order to properly space'the characters.

The hammer 25 is biasedtowardsthe shuttle 2| so that; upon depression of a printing key, the shuttle is first indexed to present the corresponding syrnbol at the printirig'point, and the hammer is released to swing forward on a-horizonta'l pivot (not shown). and strike the paper against the shuttle to form the printedimpression. After forming the impression, the hamm'er is returned to rearward position by a drive mechanism, including a springmotor- 29 intermittently wound by an electric motor 30. Movementof the hammer is controlled by a hammer escapement mechanism (not shown) which is tripped by operation of any of. the key levers: I 4. The ham-.- mer escapement mechanismis disclosed in'U. S. patent to Trego 1,965,677;

The escapement mechanism of the typewriter shown in Fig. l is shown and more completely described in U. S. patent to Norton 2,581,200 and provides for a, differential spacing of the various characters of a type font in accordance with their individual spacing requirements. This mechanism comprises a single escapement wheel and a movable dog and fixed: dog alternately engaged with the escapementwheel. Retrograde movement of the movable dog when disengaged from the escapement wheel is varied by a series of stops which may be interposed in the path of thedog'so as to limit its retrograde movement, and thus control the escapement and carriage movement 'permitted-upon. forward movement of a the dog. Forward'movement of the hammer for the printing stroke, operating through amechanical linkage, disengages the movable dog from the escapement wheel and engages the fixed dog, and return movement of the hammer re-engages the movable. dog and disengages the fixed-dog so as to permit spacing 'movementof the carriage; Adetai'led illustration and descrip tion' of "the operation'of the escapement mechanism andits control by the hammer movement is contained in the above-mentioned 'U. S; Paten According to the present invention, the typewriter describecl'in" the immediately preceding seven paragraphs is provided with mechanism for quickly and easily forming leaders and single and double rules. Fig; 2 illustrates a typicalspecimen form having leaders 3!, single rules 32-, and double rules 34%, certain of the rules'being' horizontal'and others being vertical. The form of Fig. 2 may be completely composed withia machine according to the present invention, the type shuttle 2!. being changed as" requiredv to obtain the various sizes'and'styles of typerequired. The horizontal lines are preferably typedwhile composing the written matter; and the: vertical lines are preferably formed later by removing the paper'from the carriage and reinserting it in sideways position, so that the top and bottomof the sheet are atthe sides of the. carriage.

Referring to Figs. 3 and 4; the shuttle 2| is formed of anarcuate strip 35 havingthe various type symbols embossed thereon; the strip 35' being mounted'ona fiat'web 3%. In indexingthe shuttle 2 I "when typing, the inner surface of the strip 351s moved along the surface of the anvil 22 (Fig. 1) to index the selected type symbol at the printing point 24.

Referring to Fig. 3, three rows or casesoftype symbols are providedon the'surface of the shuttle, theuppermost row "or case 31' printing the lowercase or small letters, the middlerow or case 39. printing the upper case or capital letters, and the lowermost row 40 printing:- the figures and symbols. The type shuttle is indexed either to the right or to theleft for the printing of any symbol appearing on the-type keys, leaving a vertical central zone orportion il which isin front of the printingipointi when' the shuttle is" in" its normal or unin'dexew posi- 131011.

According to the present invention; embossed symbols are formed in the zone-filof the type:

shuttle, these symbols preferably comprisingtwo" closely spaced leader dots 42 in the. lower case row of symbols 3'! for the forming ofleaderst-i' shown inFig. 2, a shorthorizontallinel liin'lthe. upper. case row'of symbols39. fori'formin sine gle rules32,.and apair'ofu'sh'ort, parallel, hori- .zontallines .45 inrthe figure: row ofsymbols'i 40 for forming double rules 34. The symbols 42, 44, and 45 may each be printed without indexing the shuttle 2! about the anvil 22, the desired symbol of the three being selected by operation or nonoperation of the cap shift key H and the figure shift key I9.

As above mentioned, a type impression is formed by forward movement of the hammer so as to drive the paper against the pigment ribbon 26 and shuttle 2i. I'he hammer 25 is normally in its rearward position and is urged forwardly towards the paper by a hammer spring (not shown) and is returned to rearward position against the bias of the hammer spring by the spring motor 29. The hammer is restrained by hammer escapement mechanism which is clearly disclosed in U. S. Patent to Trego 1,965,677, operation of the hammer escapement mechanism being controlled by the hammer escapement operating lever db. Actuation of the lever causes the hammer 25 to move forwardly for a single printing and return stroke.

Depression. of any of the key levers M first in dexes the shuttle and then actuates the lever to to release the hammer 25 and form an impression of the selected symbol. In addition, the lever to is actuated by mechanism, to be described, for forming impressions of the symbols within the central zone ti of the shuttle when the shuttle is not indexed. Forward movement of the hammer 25 in its printing stroke initiates carriage escapement for spacing movement, and return movement of the hammer completes the escape ment cycle so as to cause spacing movement of the carriage only after the printed impression has been formed. The mechanism interconnecting the hammer and the carriage escapement mechanism is illustrated and described in U. S. Patent 2,581,200.

According to the preferred form of the pres ent invention, in the printing of symbols 3?, 39, and M1 the hammer escapement operating lever it is actuated by electrical means, preferably by a solenoid l-l' operating through a link 9 and a bell crank lever pivoted on the frame 4 i, movement of the hammer in turn actuating the carriage-spacing escapement mechanism. Energizing the solenoid il serves to draw the link $9 to the right as viewed in 6, the bell crank lever 50 being rotated counterclockwise about its pivot 52 so as to depress the hammer escapement oper ating lever it and actuate the hammer escape ment mechanism to cause a printing stroke of the hammer. The spring 5!, anchored to the frame H of the typewriter, biases the bell crank lever 55, clockwise about its pivot 52 so as to return the lever 5t and link it when the solenoid 4? is no longer energized.

It is preferable when printing any of the symbols d2, it, and 5 to suppress the hammer action somewhat, so as to obtain a lighter printed impression. Accordingly, a hammer suppressor 5 1 (Figs. 6 and 7) may be linked to the bell crank lever M3, the suppressor having a bifurcated end extending on each side of a hammer check rod 55 pivoted to the hammer and extending downwardly through an opening in the frame i i. The hammer check rod 55 is drawn upwardly as the hammer moves forward to form a printed impression, and an enlargement Ell on the end of the rod is drawn upwardly against the bifurcated end 55 of the hammer suppressor to limit and arrest forward movement of the hammer. The bifurcated end 55 of the hammer suppressor may have a thinner zone 5! engaged by the enlargement -58 on the check rod 58 when printing letters and other symbols and a somewhat thicker zone '5!) moved into operating position by rotation of the bell crank lever 50 to arrest forward movement of the hammer somewhat sooner when printing the symbols 42, 6:1, and 45, so as to form a somewhat lighter impression of these latter symbols.

The spacing requirements of the symbols 42, M, and 3-5 are three arbitrary escapement or spacing units, equal to, and produced by, the rotation of the escapement wheel for a distance of three teeth. Accordingly, the escapement mechanism described in U. S. Patent 2,581,200, which is in part shown in Fig. '6, is modified to provide a projecting arm to on the three unit-space movable stop (ii. A projection -52 on the link at engages the arm 60 of the stop El as the link moves to the right (Fig. 6), so as to rotate the stop into the path of the movable dog of the escapement mechanism upon actuation of the solenoid H, which limits the carriage-spacing movement to three spacing units upon actuation of the solenoid 41.

Operation of the solenoid M is controlled by an electrical circuit, including two contact buttons M and these buttons being mounted on a boxlike housing at the right side of the keyboard (Fig. 1). Depression of the button it actuates the solenoid a single time for a single printing of or" the symbols 42, M, and 65, while actuation of the button 55 causes repeated actuation of the solenoid i l to form a leader 3!, single rule 32, or double rule 34 of any desired length. If desired, the button t5 may be depressed until the desired line is of nearly the proper length, causing rapid repeated actuation of the hammer; and then the button it may be depressed one or more times to produce a line of the exact length desired.

The wiring circuit for actuating the solenoid i? is shown in Fig. 5. This circuit includes a synchronous motor 6'! within the housing 66 in series with a single pole, single throw switch 62, biased open and closed by depressing the button 55. A rotary cam it, driven by the motor 6?, repeatedly closes a single pole, single throw switch '5 5., which is normally biased open and is in series with the switch 89 so as to successively make and break an electrical circuit through the solenoid and cause repeated operation of the solenoid. The cycle of makes and breaks or" this circuit is only a little longer than the time required for completion of the hammer cycle in forming a printed impression and return and may be operated at about six (6) makes and breaks per second. Accordingly, a printed impression is made each time this circuit is completed by the closing of switch 1 l.

A single pole, single throw switch 12, which is normally biased closed, may be mounted on the typewriter frame H (Figs. 1 and 8), this switch having a pivoted actuating arm "it in the path of a cam is settable along the usual scale 16 mounted on the front of the carriage. The earn it may be set along the scale it so as to strike the actuating arm it when the carriage has reached a predetermined position at which it is desired to stop a line. Engagement of this cam with the arm M opens the switch l2 so as to break the circuit to the motor t? and solenoid 41, thus disabling the repeat mechanism and preventing further actuation of the hammer, even though the button is maintained depressed. Accordingly, if a series of leaders or rules are to be formed with their right ends in alignment; the-cam 15: may; b.e;-v set: accordingly; andvthe button 65 depressedsoas tocause the:

machine to: form aline-of the, desired length and thenstop when ,thecarriage; 21 reaches'a predeterminedpoint.

The-button 64 controls:-a single pole, double throw switch TI, one contact of which is in series with the circuit through the switch 1 I the switch being biased-to complete-that circuit. Upon depression of. the-button 64,. the circuit through the switch It is broken and a direct circuit'is established through thesolenoiddl to energize the solenoid and cause a single printing of the symbols-.42, 44, and 45, the circuit being broken upon release-ofrthebutton164. This button may be-tusedzwhen-only one or several lines are to be formed and 1186:f 'the cam 15 is not desired.

The power for; the circuit in Fig. 5, used for energizingthe'solenoid M, may be taken from the'rsamepower source as thatused-for the intermittently electrically operated motor 30,- the motor 30 and the circuit of Fig; 5 being connectediin'parallel;

I claim:

1'. A" typewritingmachine' having'a paper carriage movable stepby-step'past a printing point, means for forming-a printed impression at the printing point, carriage-spacing mechanism for progressing the carriage" past the printing point after the forming of each impression, electrically operated-mechanism foractuating the impression-forming meansv and the carriage-spacing-mechanism, control means, including a constant-speed electric motor and a switch operated by: said motorandin circuit with said electrically operated mechanism for repeatedly completing and, opening anelectric circuit through said electrically operated mechanism to cause repeated printing of a selected type symbol, and an electric switch operated responsive to carriage positionfor opening the circuit to the electrically operated mechanism when the carriage hasreached a predetermined position.

2. A" typewriting machine having a paper carriagemovable step by step past a printing point, means for forminga printed impression at the printing'point; carriage-spacing mechanism for progressingthecarriage past the printing point after the forming ofeach impression, electrically operated'mechanism for actuating the impression-forming means and the carriage-spacing-gmechanism, control means, including a constant-speedelectric motor and a switch operated by said motor and in circuit with said electrically operated mechanism for repeatedly completing and opening an electric circuit through said; electrically operated mechanism to cause repeated printing of a selected type symbol, and an electric switch operated responsive to carriage QOSitiOILfOr-ODEIliIlg the circuit to the electri-- callyoperated mechanism, when the carriage hasreached a. predetermined position, the interval between successive completions of the circuit. to theelectrically operated mechanism being; alittle-longer, than v the time required for forming; the: printed impression and spacing movement of; the carriage.

3.,A typewriting machine having a paper carriage movable'step by'step past aprinting point, meansffor forming a printed impression at the printingpoint, carriage-spacing mechanism for progressing theq carriage; past the printing point aftenthe: forming; of: each impression; typewriter. keys foncperating;thegimpressioneformingmeans and-the carriaeerspacing mechanism-,asolenoid alternativ ly, perable gfcr. actuatine the impress sionrforming, means; and the carriage-spacing mechanism, and control means, includinga; con-,

stant-speedelectric motorand a switch operated by, said motor for repeatedly completing and opening an electric circuit through said solenoid.

to cause repeated printing of a selected type symbol, the interval between successive completions of they solenoid circuit being a little longer than the time required-for forming the printed impression and spacin movement of the carriage.

4-. A typewriting machine having a paper car-- mechanism, a switch in circuit with the solenoid for repeatedly completing and opening an electric circuit through said solenoid to cause repeated printing of a selected type symbol, a constant-speed electric motor solely driving said switch, and a switch controlling said motor.

5. A=typewriting machine having a paper-carriage movable step by step past a printing point, means for forming a printed impressionat the printin point, carriage-spacing mechanism for progressing the carriage past the printing point after the forming of each impression, a solenoid for actuating'the impression-forming means and the carriage-spacing mechanism, a switch in circuit with the solenoid for repeatedly completing and opening an electric circuit through said solenoid tocause repeated printing of a selected type symbol, a constant-speed electric motor solely driving said-switch, and 'a-sw-itch controlling said motor.

6. A typewriting machine having typewriter keys, a paper carriage movable step by step past a printing point, a-movable type shuttle mounted at the printing point, said type shuttle being arcuate in form and having type symbols embossed thereon, means for indexing said type shuttle-in either direction in response to actuation ofthe typewriter keys to present a selected symbol at the printing point, a hammer located behind the carriage and operable to drive the paper against the shuttle to form a printed impression, carriage-spacing means for progressing the carriage after forming a type impression, and means for causing operation of the hammer and spacing movement of the carriage, said type shuttle being provided with a line-forming symbol normally indexed at the printing point and moved from the printing point upon indexing of the shuttle responsive to operation of a type writer key.

7. A typewriting machine having typewriter keys, a paper carriage movable step by step past a printing point, a movable type shuttle mounted at the printing point, said type shuttle being arcuate in form and having type symbols embossed thereon, means for indexing said type shuttle in either direction in responseto actuation of the typewriter keys to present a selected symbol at the printing point, a hammer located behind the carriage and operable to drive the paper against the shuttle to. form a printedv impression, carriage-spacing.- means, for. progressing the carriage after formingwa typeimpression, and means for. causing repeated. operation of the hammer 9 and spacing movement of the carriage, said type shuttle being provided with a line-forming symbol normally indexed at the printing point and moved from the printing point upon indexing of the shuttle responsive to operation of a typewriter key.

8. A typewriting machine having typewriter keys, a paper carriage movable step by step past a printing point, a movable type shuttle mounted at the printing point, said type shuttle being arcuate in form and having type symbols embossed thereon, means for indexing said type shuttle in either direction in response to actuation of the typewriter keys to present a selected symbol at the printing point, a hammer located behind the carriage and operable to drive the paper against the shuttle to form a printed impression, carriage-spacing means for progressing the carriage after forming a type impression, means for causing repeated operation of the hammer and spacing movement of the carriage, and means operative upon the carriage reaching a predetermined point for disabling said lastmentioned means, said type shuttle being provided with a line-forming symbol normally indexed at the printing point and moved from the printing point upon indexing of the shuttle responsive to operation of a typewriter key.

9. In a rear-strike typewriter having a paper carriage, means for presenting a selected type symbol at a printing point, a hammer behind the carriage and operable to drive the paper against the type to form a printed impression, electrically operated mechanism for causing operation of the hammer and spacing movement of the carriage, control means in circuit with said electrically operated mechanism for repeatedly completing and opening an electric circuit through said electrically operated mechanism to cause repeated printing of a selected type symbol, and an electric switch operated responsive to carriage position for opening the circuit to the electrically operated mechanism when the carriage has reached a predetermined position.

10. In a rear-strike typewriter having a paper carriage, means for presenting a selected type symbol at a printing point, a hammer behind the carriage and operable to drive the paper against the type to form a printed impression, electrically operated mechanism for causing operation of the hammer and spacing movement of the carriage, means operated by said electrically operated mechanism for prematurely arresting the normal stroke of the hammer, and control means in circuit with said electrically operated mechanism for repeatedly completing and opening an electric circuit through said electrically operated mechanism to cause repeated printing of a selected type symbol.

11. A type shuttle for a rear-strike typewriting machine in which the shuttle is indexed to one side or the other in response to actuation of the typewriter keys, said type shuttle comprising: an arcuate strip having a font of type embossed thereon in two spaced groups symmetrically located one on each side of the central portion of the strip, and line-forming symbols embossed on the central portion of the strip between said two groups.

12. In a rear-strike typewriter having a paper carriage, means for presenting a selected type symbol at a printing point, a hammer behind the carriageand operable to drive the paper against the type to form a printed impression, an electrically operated mechanism for causing operation of the hammer and spacing movement of the carriage, control means in circuit with said electrically operated mechanism for repeatedly opening and closing an electrical circuit through said electrically operated mechanism to cause repeated printing of a selected type symbol, a cam settable along the length of the carriage, and an electric switch in the path of the cam for opening the circuit to the electrically operated mechanism when the carriage has reached a predetermined position.

13. A type shuttle for a rear-strike typewriting machine in which the shuttle is indexed to one side or the other in response to actuation of the typewriter keys, said type shuttle comprising: an arcuate strip having a font of type embossed thereon in two spaced groups located one on each side of the central portion of the strip, the type within each group being arranged in at least two rows and the corresponding rows of said two groups being aligned, and line-forming symbols embossed on the central portion of the strip between said two groups, each of said symbols being aligned with one of the rows of type of each group.

14. A type shuttle for a rear-strike typewriting machine in which the shuttle is indexed to one side or the other in response to actuation of the typewriter keys, said type shuttle comprising: an arcuate strip having a font of type embossed thereon in two spaced groups symmetrically located one on each side of the central portion of the strip, and at least one lineforming symbol embossed on the central portion of the strip between said two groups.

15. A typewriting machine having a paper carriage movable step by step past a printing point, means for forming a printed impression at the printing point, carriage-spacing mechanism for progressing the carriage past the printing point after the forming of each impression, a solenoid for actuating the impression-forming means and the carriage-spacing mechanism, a first electric circuit to the solenoid, a constantspeed electric motor, a switch operated by the motor and in the first solenoid circuit for repeatedly completing and interrupting said circuit, an electric circuit to the motor, a manually operated switch in the motor circuit for controlling operation of the motor, a second electric circuit to the solenoid, and a multiposition switch common to both circuits to the solenoid, biased to complete the first circuit and operable to interrupt the first circuit and complete the second circuit.

16. A typewriting machine as claimed in claim 15, having a switch in the first solenoid circuit, said switch being biased to closed position and opened in response to movement of the paper carriage upon the carriage reaching a predetermined position.

GEORGE E. CANHAM.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,142,151 Duiven June 8, 1915 1,889,315 Henderson Nov. 29, 1932 2,287,100 Hediger June 23, 1942 2,548,717 Gates. Jr. ...l-...... Apr. 10, .1951 

